I hope I understood you correctly. Here is what the macro does.

When you try it remember to make changes to the config area of the code.
Sub NumberSequence()
Dim input_one As String, input_two As String, input_three As String
Dim target As String, main As String, col_start As String
Dim col_start_number As Long, substract As Long
Dim next_row As Long, next_number As Long
'CONFIG HERE
'---------------------------------------
'ranges of form inputs
input_one = "B3"
input_two = "C3"
input_three = "D3"
'first column where data starts in target sheet
col_start = "A"
'from what row do you want to start counting?
substract = 3
'names of sheets
target = "target"
main = "form"
'---------------------------------------
'convert the letter of the column to a number
col_start_number = Range(col_start & 1).Column
'get next empty row in target sheet
next_row = _
Sheets(target).Cells(Rows.Count, col_start_number).End(xlUp).row + 1
'next number in the sequence
next_number = next_row - substract + 1
With Sheets(target)
'transfer the sequencial number
.Cells(next_row, col_start_number) = next_number
'transfer the inputs of the form
.Cells(next_row, col_start_number + 1) = _
Sheets(main).Range(input_one)
.Cells(next_row, col_start_number + 2) = _
Sheets(main).Range(input_two)
.Cells(next_row, col_start_number + 3) = _
Sheets(main).Range(input_three)
End With
End Sub